Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $69.50   9.490%   $76.0956   $76.10   $76.10   $76.10  
  Purchase #2 $32.85   8.195%   $35.5421   $35.54   $35.55   $35.50  
  Purchase #3 $60.85   10.103%   $66.9977   $67.00   $67.00   $67.00  
  Purchase #4 $71.53   8.626%   $77.7002   $77.70   $77.70   $77.70  
  Purchase #5 $7.69   8.393%   $8.3354   $8.34   $8.35   $8.30  
  Purchase #6 $8.47   4.490%   $8.8503   $8.85   $8.85   $8.90  
  Purchase #7 $69.77   7.710%   $75.1493   $75.15   $75.15   $75.10  
  7 purchase totals = $320.66       $348.6706   $348.68   $348.70   $348.60